Air Pollution and Pollutant Gases in the World | Reasons and Effects

Air pollution is a challenged to the world and lot of actions are being taken to minimize effects due to this air pollution. There are a lot of air pollutants including toxic gaseous compounds. These air pollutants are manly formed due to human activities and effect to the humans and environment. Acid rains, photochemical smog and ozone depletion are few examples to air pollution. Effects of air pollutants can be short term or long time.


  • List of air pollutant gases
  • How air pollutant gases are generated due to human activities
    • Industrialization
    • Automobiles
    • Power generation
  • Effects of air pollutant gases
    • Effects to humans due to air pollutant gases
    • Effects to the environment due to air pollutant gases
  • How to control air pollution and emission of air pollutant gases
  • International standards for emitting air pollutant gases to the atmosphere

List of air pollutant gases

There are a lot of air pollutant gases as listed below. Most of these gases are produced due to human activities.

  • Carbon monoxide (CO)
  • Carbon dioxide (CO2)
  • Methane (CH4)
  • Sulfur dioxide (SO2)
  • Sulfur trioxide (SO3)
  • Hydrogen sulphide(H2S)
  • Oxides of nitrogen (NOx)
  • Ozone (O3)
  • Hydrocarbons
  • Ammonia

How air pollutant gases are generated due to human activities

Here we will study how these air pollutant gases are generated due to following reasons.

  • Industrialization
  • Automobiles
  • Power generation

Carbon monoxide (CO)

  • Automobiles: Carbon monoxide is a highly toxic gas and mainly emitted due to emission of automobiles. Incomplete combustion of fuel (lack of oxygen supply) will cause the formation of carbon monoxide except carbon dioxide gas. Chemically, Carbon monoxide is a Colourless, odourless and tasteless gas and it is not soluble in water.
  • Industrial: Carbon monoxide gas is deliberately produced for some industrial applications such as Iron extraction because Carbon monoxide can behave as a reducing agent.

Carbon dioxide (CO2)

  • The most generated chemical after a combustion product of fuels is the Carbon dioxide gas. Automobiles, industries and power generation emit Carbon dioxide gas in a greater quantity.

Sulfur dioxide (SO2)

  • Power generation:Sulfur dioxide gas is generated due to combustion of fuel which contain sulfur. Specially, coal has a higher sulfur content as a fuel. Therefore, coal power plants generated higher quantity of Sulfur dioxide gas.
  • Automobile: Automobiles which use diesel generated more sulfur dioxide gas compared to petrol driven vehicles.
  • Industries: Industries burns fuels for heat requirements (in boilers and furnaces) and Sulfur dioxide gas is released to the atmosphere.

Sulfur trioxide (SO3)

Usually, Sulfur trioxide gas is not directly generated as an emission. Sulfur dioxide gas is converted to Sulfur trioxide gas by reacting with oxygen gas.

Hydrogen sulphide (H2S)

Hydrogen sulfide gas is highly toxic gas and very low concentrations is enough to cause severe injuries or death. Therefore, usually we cannot observe significant concentrations of Hydrogen sulfide gas in the atmosphere.

  • Industrial and Power generation: Hydrogen sulfide gas is mainly generated due to the refining of petroleum products. But, this Hydrogen sulfide gas is burnt or converted to other useful chemical by-products in the refining plant. Therefore very less quantity of Hydrogen sulfide gas is released to the environment.
  • Natural formation: Hydrogen sulfide gas is naturally formed due to anaerobic digestion.

Oxides of nitrogen (NOx)

There are lot of oxides of nitrogen and they are produced according to the existing conditions. Most times, Nitric oxide (NO) and nitrogen dioxide (NO2) gases are generated.

  • Power generation and industry: Combustion of nitrogen containing fuels in a higher temperature produces nitric oxide gas. If more oxygen is available, Nitric oxide is oxidized to Nitrogen dioxide gas.
  • Nitrogen dioxide gas is accumulated in cities and towns where lot of vehicles are being moved.


Though Ozone layer protect the earth from dangerous UV rays, it is a toxic gas at surface level. However, Ozone gas is not generated directly. But due to formation of free radicals due to other chemicals in the atmosphere will generate Ozone gas. This is happened in photochemical smog.


  • Automobiles: When fuels (diesel and petrol) are not completely burnt in internal combustion engines, unburnt hydrocarbons are emitted to the atmosphere through the exhaust pipe. This is happened when air supply is not sufficient to burn the provided quantity of fuel in to the engine cylinder.

Effects to humans, animals and environment of air pollutant gases

Air pollution negatively effects to the human lifestyle, animals and natural environment. Those negative impacts are already can be seen throughout the world and continuous monitoring is a must to minimize or avoid such negative impacts.

Effects of toxic gases

Toxic gases such as Carbon monoxide, Hydrogen sulfide are extremely toxic gases. Minor quantities of these gases can give very dangerous results.

Effects of Acid rains

Sulfur dioxide and nitrogen dioxide: Both these gases are acidic gases and capable of forming acid rains. These acid rain can be harmful to human skin. Acidity of ground water and surface water can be increased and that may cause problems to drinking water.

Effects of Global warming

Green house gases increases the temperature of world. Methane, carbon dioxide, nitrogen dioxide are several greenhouses gases. Global warming results in sea level rises due to glacier melting.

Photochemical smog

Photochemical smog is caused due to automobile exhaust in cities where huge traffics are. Effects of photochemical smog is mentioned below. There are series of toxic compounds such as ozone, aldehydes, PAN, hydrocarbons, Nitrogen dioxide when photochemical smog exist.

  1. Ozone can cause coughing, wheezing, bronchial constriction and irritation to the respiratory mucous system.
  2. Aldehyde and PAN cause to irritation of eyes.
  3. Reduces visibility
  4. Cause to several chronic diseases of eyes, heart, and lungs.
  5. Affects to the human health and comfort.
  6. Affects to growth of plants. Ozone damages to plants and reduces crop. PAN has also highest toxicity to plants. It attacks younger leaves and causes bronzing and glazing of their surfaces.
  7. Materials are also affected by photochemical smog. As an example, Rubber is cracked.

How to control air pollution and emission of air pollutant gases

We can control air pollution by taking proper actions minimizing emission of pollutant gases. We can see what are the alternatives to minimize air pollutants due to industry, power generation and automobiles.

Reduce air pollutant gases in industry and power generation

  • Use low sulfur fuels: This will help to avoid or minimize emission of sulfur dioxide gas.
  • Installing flue gas treatment systems: Acid gas controlling units, bag filters, activated carbon systems, dry reactors, scrubbers will catch acidic gases and particulate matter and control the emission.
  • Encourage and develop to go for solar, wind and other sustainable energy sources

Reduce air pollutant gases in automobiles

  • Encourage electronic vehicles instead of petroleum fuel based vehicles
  • Installing catalyst reactor to exhaust system to convert higher toxic emissions to lower toxic emissions (Example: converting carbon monoxide to carbon dioxide).
  • Constructing by-pass roads or highways to minimize traffic
  • Encourage and develop public transport facilities to minimize personal vehicles


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